U.S. patent application number 16/492811 was filed with the patent office on 2020-05-07 for ultraviolet curable black ink composition for foldable display and bezel pattern forming method using same.
This patent application is currently assigned to LG Chem, Ltd.. The applicant listed for this patent is LG Chem, Ltd.. Invention is credited to Areum Kim, Joonhyung Kim, Sungeun Park, Jaehyun Yoo.
Application Number | 20200140705 16/492811 |
Document ID | / |
Family ID | 67056248 |
Filed Date | 2020-05-07 |
United States Patent
Application |
20200140705 |
Kind Code |
A1 |
Yoo; Jaehyun ; et
al. |
May 7, 2020 |
Ultraviolet Curable Black Ink Composition for Foldable Display and
Bezel Pattern Forming Method Using Same
Abstract
An ultraviolet curable black ink composition, a bezel pattern
forming method using the same, a bezel pattern produced by the
method, and a display substrate comprising the bezel pattern are
disclosed herein. In some embodiments, an ultraviolet curable ink
composition comprises a black pigment, a dispersant, an epoxy
compound, an oxetane compound, a light diffusing agent, a
photopolymerization initiator, and an organic solvent. The
ultraviolet curable black ink composition is developed to be
applied to a cover window film of a foldable display, has excellent
light shielding properties and folding properties at a thin
thickness, and as a light diffusing agent is applied to the ink,
prevents surface wrinkles from generating due to a difference in
the curing rate of the upper and lower portions of a bezel, by
means of UV curing alone without a pretreatment process.
Inventors: |
Yoo; Jaehyun; (Daejeon,
KR) ; Park; Sungeun; (Daejeon, KR) ; Kim;
Areum; (Daejeon, KR) ; Kim; Joonhyung;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG Chem, Ltd. |
Seoul |
|
KR |
|
|
Assignee: |
LG Chem, Ltd.
Seoul
KR
|
Family ID: |
67056248 |
Appl. No.: |
16/492811 |
Filed: |
December 11, 2018 |
PCT Filed: |
December 11, 2018 |
PCT NO: |
PCT/KR2018/015664 |
371 Date: |
September 10, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41J 11/002 20130101;
B41M 7/0081 20130101; C09D 11/36 20130101; C09D 11/322 20130101;
C09D 11/101 20130101; C09D 11/38 20130101; C09D 11/037 20130101;
C09D 11/324 20130101 |
International
Class: |
C09D 11/101 20060101
C09D011/101; B41M 7/00 20060101 B41M007/00; B41J 11/00 20060101
B41J011/00; C09D 11/037 20060101 C09D011/037; C09D 11/322 20060101
C09D011/322 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2017 |
KR |
10-2017-0171970 |
Dec 10, 2018 |
KR |
10-2018-0157794 |
Claims
1. An ultraviolet curable ink composition for forming a black bezel
pattern, comprising a black pigment; a dispersant; an epoxy
compound; an oxetane compound; a light diffusing agent; a
photopolymerization initiator; and an organic solvent.
2. The ultraviolet curable ink composition according to claim 1,
wherein the light diffusing agent comprises TiO.sub.2,
Al.sub.2O.sub.3 or a combination thereof.
3. The ultraviolet curable ink composition according to claim 1,
wherein the organic solvent has a boiling point of 200.degree. C.
or higher and a viscosity of 1 cP to 5 cP at 25.degree. C.
4. The ultraviolet curable ink composition according to claim 1,
wherein the photopolymerization initiator is
10-[1,1'-biphenyl]-4-yl-2-(1-methylethyl)-9-oxo-9H-thioxanthenium
hexafluorophosphate.
5. The ultraviolet curable ink composition according to claim 1,
wherein of the black pigment is present in an amount of 15 to 20%
by weight based on the total weight of the ultraviolet curable ink
composition.
6. The ultraviolet curable ink composition according to claim 1,
wherein the organic solvent is present in an amount of 20 to 40% by
weight based on the total weight of the ultraviolet curable ink
composition.
7. The ultraviolet curable ink composition according to claim 1,
wherein the composition has a viscosity of 1 cP to 50 cP at
25.degree. C., and wherein the adhesive force to a substrate of the
composition after curing is 4B or more as measured by ASTM D3002 or
D3359 in a cross-cut test.
8. The ultraviolet curable ink composition according to claim 1,
wherein the composition has a curing dose of 1000 to 10,000
mJ/cm.sup.2 and is cured by absorbing ultraviolet radiation in a
wavelength range of 250 nm to 410 nm.
9. A method of forming a bezel pattern, comprising: inkjet printing
the ultraviolet curable ink composition of claim 1 on a substrate
in the form of a bezel pattern; and irradiating the printed
ultraviolet curable ink composition with ultraviolet radiation to
cure the bezel pattern.
10. The method of forming a bezel pattern according to claim 9,
wherein the thickness of the cured bezel pattern is 2 to 4
.mu.m.
11. A bezel pattern produced by patterning and curing the
ultraviolet curable ink composition of claim 1.
12. A display substrate comprising the bezel pattern of claim
11.
13. The ultraviolet curable ink composition according to claim 1,
wherein the light diffusing agent is present in an amount of 5 to
10% by weight based on the total weight of the ultraviolet curable
ink composition.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This application claims priorities to Korean Patent
Application Nos. 10-2017-0171970, filed on Dec. 14, 2017 and
10-2018-0157794, filed on Dec. 10, 2018, the disclosures of which
are incorporated herein by reference.
[0002] The present invention relates to an ultraviolet curable
black ink composition for a foldable display, a method of forming a
bezel pattern by using the same, a bezel pattern manufactured
thereby, and a display substrate comprising the same.
2. Description of the Related Art
[0003] The flexible display market has evolved into foldable
products that can be freely folded and unfolded in both flat and
curved products. Like other display devices, the foldable display
requires a bezel pattern for imparting color, while patterns in the
non-display area of the panel are not visually recognized. Mobile
devices come in close proximity to human eyes due to their
nature.
[0004] Therefore, in order to prevent the panel pattern from being
visible, a bezel having a high light-shielding property must be
formed. However, when the bezel becomes thick, there arises a
problem that the stepped bezel is visually recognized on the
screen. In order to solve this problem, a bezel pattern having
excellent light-shielding property at a thin thickness is required
and also an ink composition capable of suppressing surface
wrinkling is required to perform single layer printing of a high
light-shielding black ink and its curing with UV at once.
[0005] Korean Patent Application Laying-open No. 10-2016-0147535
has disclosed an ultraviolet curable black ink enabling to form a
bezel by an inkjet process. However, the ink is intended to be
applied to TV products and has a low light-shielding property
(optical density (OD) 1 @2.2 .mu.m) so that it is difficult to
apply it to foldable products due to problems of panel pattern
visibility. Korean Patent Application Laying-open No.
10-2016-0046723 has disclosed an ink that has a high
light-shielding property through single layer printing, but a heat
treatment process was applied before UV curing to suppress surface
wrinkling. In addition, the inks disclosed in the above prior art
documents are bezel inks developed for application to glass
substrates and are difficult to apply to a foldable cover window
film.
[0006] Accordingly, it is required to a develop a black bezel ink
for application to a cover window film of a foldable display, which
has excellent light-shielding properties and folding properties at
a thin thickness and in which by introducing a light diffusing
agent to the ink, surface wrinkling due to difference in curing
rate between the upper and lower portions of the bezel can be
suppressed even with UV curing alone without any pretreatment
process.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide an
ultraviolet curable black ink composition, which is a black bezel
ink which has developed for application to a cover window film of a
foldable display and has excellent light-shielding properties and
folding properties at a thin thickness and by introducing a light
diffusing agent thereto, surface wrinkling due to difference in
curing rate between the upper and lower portions of the bezel can
be suppressed even with UV curing alone without any pretreatment
process. In addition, the present invention is intended to provide
a method of forming a bezel pattern by using the same, a bezel
pattern manufactured thereby, and a display substrate comprising
the same.
[0008] In order to achieve the above object, the present invention
provides an ultraviolet curable ink composition for forming a black
bezel pattern, comprising a black pigment, a dispersant; an epoxy
compound; an oxetane compound; a light diffusing agent; a
photopolymerization initiator; and an organic solvent.
[0009] Also, the present invention provides a method of forming a
bezel pattern by using the ultraviolet curable ink composition,
comprising the steps of: a) inkjet printing the ultraviolet curable
ink composition on a substrate to form a bezel pattern; and b)
irradiating the bezel pattern with ultraviolet rays to cure it. The
present invention also provides a bezel pattern produced by using
the ultraviolet curable ink composition.
[0010] The present invention also provides a display substrate
comprising the bezel pattern.
Effect of the Invention
[0011] The ultraviolet curable black ink composition according to
the present invention is a black bezel ink which has developed for
application to a cover window film of a foldable display. It has
excellent light-shielding properties at a thin thickness so that
the problem of pattern visibility in the panel and visibility
problems due to the stepped portion are not generated. By
introducing light diffusing agent to the ink, surface wrinkling due
to difference in curing rate between the upper and lower portions
of the bezel can be suppressed even with UV curing alone without
any pretreatment process.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Hereinafter, the present invention will be described in more
detail.
[0013] Since various modifications and variations can be made in
the present invention, particular embodiments are illustrated in
the drawings and will be described in detail in the detailed
description. It should be understood, however, that the invention
is not intended to be limited to the particular embodiments, but
includes all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention. In the following
description of the present invention, detailed description of known
functions will be omitted if it is determined that it may obscure
the gist of the present invention.
[0014] The ultraviolet curable ink composition according to the
present invention comprises a black pigment, a dispersant; an epoxy
compound; an oxetane compound; a light diffusing agent; a
photopolymerization initiator; and an organic solvent.
[0015] The black pigment comprises at least one black ink pigment
selected from the group consisting of carbon black, graphite, metal
oxide, organic black pigment.
[0016] Examples of carbon black include Cisto 5HIISAF-HS, Cisto KH,
Cisto 3HHAF-HS, Cisto NH, Cisto 3M, Cisto 300HAF-LS, Cisto
116HMMAF-HS, Cisto 116MAF, Cisto FMFEF-HS, Cisto SOFEF, Cisto VGPF,
Cisto SVHSRF-HS, and Cisto SSRF (Donghae Carbon Co., Ltd.); Diagram
black II, Diagram black N339, Diagram black SH, Diagram black H,
Diagram LH, Diagram HA, Diagram SF, Diagram N550M, Diagram M,
Diagram E, Diagram G, Diagram R, Diagram N760M, Diagram LR, #2700,
#2600, #2400, #2350, #2300, #2200, #1000, #980, #900, MCF88, #52,
#50, #47, #45, #45L, #25, #CF9, #95, #3030, #3050, MA7, MA77, MA8,
MA11, MA100, MA40, OIL7B, OIL9B, OIL11B, OIL30B and OIL31B
(Mitsubishi Chemical Corporation); PRINTEX-U, PRINTEX-V,
PRINTEX-140U, PRINTEX-140V, PRINTEX-95, PRINTEX-85, PRINTEX-75,
PRINTEX-55, PRINTEX-45, PRINTEX-300, PRINTEX-35, PRINTEX-25,
PRINTEX-200, PRINTEX-40, PRINTEX-30, PRINTEX-3, PRINTEX-A, SPECIAL
BLACK-550, SPECIAL BLACK-350, SPECIAL BLACK-250, SPECIAL BLACK-100
and LAMP BLACK-101 (Degussa Co., Ltd.); RAVEN-1100ULTRA,
RAVEN-1080ULTRA, RAVEN-1060ULTRA, RAVEN-1040, RAVEN-1035,
RAVEN-1020, RAVEN-1000, RAVEN-890H, RAVEN-890, RAVEN-880ULTRA,
RAVEN-860ULTRA, RAVEN-850, RAVEN-820, RAVEN-790ULTRA,
RAVEN-780ULTRA, RAVEN-760ULTRA, RAVEN-520, RAVEN-500, RAVEN-460,
RAVEN-450, RAVEN-430ULTRA, RAVEN-420, RAVEN-410, RAVEN-2500ULTRA,
RAVEN-2000, RAVEN-1500, RAVEN-1255, RAVEN-1250, RAVEN-1200,
RAVEN-1190ULTRA, and RAVEN-1170 (Columbia Carbon Co.), mixtures
thereof, or the like.
[0017] As the organic black pigment, aniline black, lactam black,
or perylene black series may be used, but the organic black pigment
is not limited thereto.
[0018] The content of the black pigment is 15 to 25 wt %,
preferably 15 to 20 wt % based on the total ink composition. If the
content is less than 15 wt % based on the total ink composition, a
level of OD applicable to the bezel is not obtained. If the content
is more than 25 wt %, an excess amount of colorant may not be
dispersed in the ink and precipitates may be formed.
[0019] The dispersant is used to make the black pigment particles
of uniform size, and also to reduce the production time of the ink.
As the dispersant, a polymeric, nonionic, anionic or cationic
dispersant may be used. Examples thereof include acrylics,
polyalkylene glycols and esters thereof, polyoxyalkylene polyhydric
alcohols, ester alkylene oxide adducts, alcohol alkylene oxide
adducts, sulfonic esters, sulfonates, carboxylic esters,
carboxylates, alkylamide alkylene oxide adducts, alkylamines and
the like. These may be used alone or in combination of two or more.
Among them, it is preferable to use an acrylic-based dispersant
which is excellent in storage stability of ink.
[0020] The content of the dispersant is 0.5 to 5 wt %, or 2 to 4 wt
% based on the total ink composition. When the content of the
dispersant is less than 0.5 wt %, the pigment may not uniformly be
dispersed. When it exceeds 5 wt %, the pigment may be aggregated or
the curing sensitivity may be lowered.
[0021] The epoxy compound is a cationic polymerizable component,
specifically at least one selected from a bisphenol-based epoxy
compound, a novolak-based epoxy compound, a glycidylester-based
epoxy compound, a glycidylamine-based epoxy compound, a linear
aliphatic epoxy compound, a biphenyl type epoxy compound and an
alicyclic epoxy compound.
[0022] The alicyclic epoxy compound may refer to a compound
containing at least one epoxidized aliphatic cyclic group.
[0023] In the alicyclic epoxy compound containing epoxidized
aliphatic cyclic group(s), the epoxidized aliphatic cyclic group
refers to an epoxy group bonded to an alicyclic ring. Examples
thereof include a functional group such as a 3,4-epoxycyclopentyl
group, a 3,4-epoxycyclohexyl group, a 3,4-epoxycyclopentylmethyl
group, a 3,4-epoxycyclohexylmethyl group, a
2-(3,4-epoxycyclopentyl)ethyl group, a 2-(3,4-epoxycyclohexyl)ethyl
group, a 3-(3,4-epoxycyclopentyl)propyl group or a
3-(3,4-epoxycyclohexyl)propyl group. The hydrogen atom constituting
the alicyclic ring may be optionally substituted with a substituent
such as an alkyl group. The alicyclic epoxy compound includes the
compounds specifically exemplified below, but is not limited to
thereto.
[0024] There may be used, for example, dicyclopentadiene dioxide,
cyclohexene oxide, 4-vinyl-1,2-epoxy-4-vinylcyclohexene,
vinylcyclohexene dioxide, limonene monoxide, limonene dioxide,
(3,4-epoxycyclohexyl)methyl-3,4-epoxycyclohexane carboxylate,
3-vinylcyclohexene oxide, bis(2,3-epoxycyclopentyl)ether,
bis(3,4-epoxycyclohexylmethyl)adipate,
bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,
(3,4-epoxycyclohexyl)methyl alcohol,
(3,4-epoxy-6-methylcyclohexyl)methyl-3,4-epoxy-6-methylcyclohexane
carboxylate, ethylene glycol bis(3,4-epoxycyclohexyl)ether,
3,4-epoxycyclohexene carboxylic ethylene glycol diester,
(3,4-epoxycyclohexyl)ethyltrimethoxysilane, Celloxide 8000 and
Celloxide 2021P (manufactured by Daicel Corporation).
[0025] The content of the epoxy compound is preferably 3 to 60 wt
%, more preferably 5 to 30 wt % based on the total weight of the UV
curable ink composition. If the content of the epoxy compound
exceeds 60 wt %, viscosity of the ink composition is increased, and
thus the performance of the inkjet process may be deteriorated. If
the content is less than 3 wt %, curing sensitivity may be
reduced.
[0026] The oxetane compound is a cationic polymerizable monomer,
which is a compound having a quaternary cyclic ether group in its
molecular structure, and may serve to lower the viscosity of the
cationic cured ink composition, for example, to less than 50 cPs at
25.degree. C.
[0027] In particular, there may be exemplified by
3-ethyl-3-hydroxymethyl oxetane,
1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene,
3-ethyl-3-(phenoxymethyl)oxetane,
di[(3-ethyl-3-oxetanyl)methyl]ether,
3-ethyl-3-(2-ethylhexyloxymethyl)oxetane,
3-ethyl-3-cyclohexyloxymethyl oxetane or phenol novolak oxetane.
Examples of the oxetane compound include "ARON OXETANE OXT-101",
"ARON OXETANE OXT-121", "ARON OXETANE OXT-211", "ARON OXETANE
OXT-221", "ARON OXETANE OXT-212" and the like. These may be used
alone or in combination of two or more.
[0028] The content of the oxetane compound is preferably 15 to 80
wt %, more preferably 20 to 60 wt % based on the total weight of
the UV curable ink composition. If it is more than 80 wt %, curing
sensitivity is low, and if it is less than 15 wt %, the viscosity
increases and coating properties is reduced.
[0029] The light diffusing agent may be TiO.sub.2 or
Al.sub.2O.sub.3 or a combination thereof as a material having a
high surface reflectivity and is used to suppress surface wrinkling
that occurs when an ink composition having high light-shielding
characteristics (e.g., O.D 5) as in the present invention is single
layer printed and UV cured.
[0030] The light diffusing agent may have an average particle
diameter of 0.1 to 5.0 .mu.m.
[0031] The content of the light diffusing agent may be 5 to 10 wt
%, and preferably 5 to 8 wt % based on the total weight of the UV
curable ink composition. When the content of the light diffusing
agent is less than 5 wt %, the light diffusing effect is lowered
and surface wrinkling are occurred during UV curing. When the
content of the light diffusing agent is more than 10 wt %, the
content of inorganic filler is increased, causing the deteriorated
inkjet processability.
[0032] The photopolymerization initiator is a cationic
polymerizable initiator. Specifically, the photopolymerization
initiator comprises a compound which produces cationic species or
Bronsted acid by irradiation with ultraviolet rays, for example, at
least one of iodonium and sulfonium salts. The iodonium or the
sulfonium salt causes a curing reaction in which monomers having
unsaturated double bond(s) contained in the ink are reacted to
produce a polymer during UV curing process. As an example, the
photopolymerization initiator may be a photopolymerization
initiator having an anion represented by SbF.sub.6.sup.-,
AsF.sub.6.sup.-, BF.sub.6.sup.-, (C.sub.6F.sub.5).sub.4B.sup.-,
PF.sub.6.sup.- or Rf.sub.nF.sub.6-n, but is not limited thereto.
Commercially available products include Irgacure 250, Irgacure 270,
Irgacure 290, CPI-100P, CPI-101A, CPI-210S, Omnicat 440, Omnicat
550, Omnicat 650 and the like. These photopolymerization initiators
may be used alone or in combination of two or more. In particular,
in one embodiment of the present invention, in order to improve
storage stability of the ultraviolet curable ink composition, the
photopolymerization initiator may be a sulfonium salt, more
preferably
10-[1,1'-biphenyl]-4-yl-2-(1-methylethyl)-9-oxo-9H-thioxanthenium
hexafluorophosphate) (Omnicat 550).
[0033] The content of the photopolymerization initiator is 1 to 10
wt %, preferably 2 to 7 wt %, more preferably 3 to 5 wt % based on
the total ink composition. When the content of the
photopolymerization initiator is less than 1%, the curing reaction
may be insufficient, and when the content is more than 10 wt %, it
may not be dissolved completely, or the viscosity may be increased
so that the inkjet processability may be deteriorated.
[0034] The organic solvent may be used without particular
limitation as long as it has excellent curing sensitivity even
after printing the bezel pattern on the display substrate by using
the ink composition according to the present invention. However, in
order to improve the performance of the inkjet process, it is
preferable to use an organic solvent having a viscosity of 1 cP to
5 cP, preferably 3 cP or less at 25.degree. C.
[0035] That is, when the black pigment is contained at a low
content of less than 10 wt % (particularly 7 wt % or less) with
respect to the total ink composition, there is no problem in the
performance of the inkjet process even if an organic solvent such
as ethylene glycol monobutyl ether acetate (BCsA) having a boiling
point of less than 200.degree. C. is used. However, when the black
pigment is contained in the ink composition in an amount of 10 wt %
or more, the performance of the inkjet process is deteriorated.
[0036] Therefore, in the present invention, it is required to use
an organic solvent capable of enhancing or improving the
performance of the inkjet process by allowing the ink composition
to form a bezel pattern having a thin thickness while exhibiting
high light-shielding performance. The performance of the inkjet
process is improved as the organic solvent satisfying conditions of
the high boiling point and the low viscosity described above
(boiling point of 200.degree. C. or higher and viscosity at
25.degree. C. of 1 cP to 5 cP, particularly 3 cP or lower) is used.
Accordingly, an organic solvent satisfying such conditions, for
example, an organic solvent such as butyl diglyme (diethylene
glycol dibutyl ether), dipropylene glycol methyl ether acetate,
ethylene glycol dibutyrate, diethyl succinate, gamma-butyrolactone
(GBL) and ethyl caprate should be used. It is most preferable to
use butyl diglyme and diethyl succinate.
[0037] The content of the organic solvent is 10 to 40 wt %,
preferably 20 to 35 wt %, more preferably 25 to 35 wt % based on
the total ink composition. When the content of the organic solvent
is less than 10 wt %, the viscosity of the ink may increase or the
thickness of the bezel layer may increase. When the content of the
organic solvent exceeds 40 wt %, the curing sensitivity may be
lowered.
[0038] Meanwhile, the ink composition according to the present
invention may further comprise at least one of a reactive diluent,
an adhesion promoting agent, and a surfactant, if necessary.
[0039] The reactive diluent may be included to lower the viscosity
of the ink to improve inkjet processability. A cationic
polymerizable glycidyl ether-based epoxy compound can be used.
Examples of the glycidyl ether-based epoxy compound include N-butyl
glycidyl ether, neopentyl glycol diglycidyl ether (LD203) and the
like, and one or more thereof can be used.
[0040] The content of the reactive diluent is preferably 0 to 30 wt
%, more preferably 0.1 to 20 wt % based on the total weight of the
ultraviolet curable ink composition. If it is more than 30 wt %,
the curing sensitivity is lowered.
[0041] The adhesion promoting agent can improve adhesion between
the substrate and the printing layer. It may be at least one
selected from the group consisting of an alkoxysilane compound and
a phosphate-based acrylate compound such as phosphate acrylate.
Examples of the alkoxysilane compound include 3-glycidoxypropyl
trimethoxysilane (KBM-403, Shin-Etsu Silicones of America),
3-glycidoxypropyl methyldimethoxysilane (KBM-402),
2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane (KBM-303),
3-glycidoxypropyl methyldiethoxysilane (KBE-402), 3-glycidoxypropyl
triethoxysilane (KBE-403) and 3-methacryloxypropyl trimethoxysilane
(KBM-503), and one or more of them can be used.
[0042] When the adhesion promoting agent is used, the content
thereof is 1 to 5 wt %, preferably 2 to 4 wt % based on the total
ink composition. When the content of the adhesion promoting agent
is less than 1 wt %, the adhesion between the substrate and the
printing layer may be reduced. When the content is more than 5 wt
%, the stability of the ink and curing sensitivity may be
deteriorated.
[0043] The surfactant modulates the surface tension of the ink to
enable smooth jetting and to allow the ink to be properly spread on
the substrate. For example, it may be selected from the group
consisting of Megafack F-444, F-475, F-478, F-479, F-484, F-550,
F-552, F-553, F-555, F-570 and RS-75 from DIC (DaiNippon Ink &
Chemicals), or Surflon S-111, S-112, S-113, S-121, S-131, S-132,
S-141 and S-145 from Asahi Glass Co., Ltd., or Fluorad FC-93,
FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430 and FC-4430 from
Sumitomo 3M Co., Ltd., or Zonyl FS-300, FSN, FSN-100 and FSO from
DuPont, or BYK-306, BYK-310, BYK-320, BYK-331, BYK-333, BYK-342,
BYK-350, BYK-354, BYK-355, BYK-356, BYK-358N, BYK-359, BYK-361N,
BYK-381, BYK-370, BYK-371, BYK-378, BYK-388, BYK-392, BYK-394,
BYK-399, BYK-3440, BYK-3441, BYKETOL-AQ, BYK-DYNWET 800,
BYK-SILCLEAN 3700 and BYK-UV 3570 from BYK, or Rad 2100, Rad 2011,
Glide 100, Glide 410, Glide 450, Flow 370 and Flow 425 from TEGO,
etc. These may be used singly or in combination of two or more.
[0044] If the surfactant is included in the ink composition, the
content thereof is 0.1 to 5 wt %, preferably 0.5 to 3 wt % based on
the total ink composition. If the content of the surfactant is less
than 0.1 wt %, the effect of lowering the surface tension of the
composition may be insufficient, resulting in coating failure when
the composition is coated on the substrate. If the content is more
than 5.0 wt %, the surfactant may be used in an excessive amount,
resulting in a problem that the compatibility and the antifoaming
property of the composition would rather be reduced.
[0045] The UV curable ink composition used in the present invention
spreads within a short time after inkjet printing to exhibit
excellent coating properties, and exhibits excellent adhesion
properties by curing. Therefore, when the UV curable ink
composition is applied to the inkjet printer, it is preferable to
provide a UV lamp just behind the inkjet head so that curing can be
performed simultaneously with inkjet printing.
[0046] The UV curable ink composition has a curing dose of 1 to
10,000 mJ/cm.sup.2, preferably 1,000 to 2,000 mJ/cm.sup.2.
[0047] The UV curable ink composition is cured by absorbing
ultraviolet radiation in a wavelength range of 250 nm to 450 nm,
preferably 360 nm to 410 nm.
[0048] The UV curable ink composition, for example, having a
viscosity of 1 to 50 cP at 25.degree. C., more preferably 3 to 45
cP at 25.degree. C., is suitable for the inkjet process. The UV
curable ink composition having the above-described viscosity range
has good ejection at a process temperature. The process temperature
means a temperature heated in order to lower viscosity of the
curable ink composition. The process temperature may be from
10.degree. C. to 100.degree. C., and preferably from 20.degree. C.
to 70.degree. C.
[0049] The ultraviolet curable ink composition has excellent
adhesion to a substrate and coating property.
[0050] In addition, the bezel pattern formed according to the
present invention with the UV curable ink composition is excellent
in adhesion to a substrate. Also, the adhesive force to a substrate
when a post-process (heat treatment) is not included is 4B or more
in a cross-cut test.
[0051] Next, a method of forming a bezel pattern by using the
ultraviolet curable ink composition according to the present
invention will be described. The method of forming a bezel pattern
by using the ultraviolet curable ink composition comprises the
steps of: a) inkjet printing the ultraviolet curable ink
composition on a substrate to form a bezel pattern; and b)
irradiating the bezel pattern with ultraviolet rays to cure it.
Here, the thickness of the cured bezel pattern may be 2 to 6 .mu.m,
or 2 to 4 .mu.m. A detailed description thereof refers to
descriptions about the ink composition as described above and the
method of forming a bezel pattern by using a conventional cationic
polymerizable ink composition.
[0052] Meanwhile, the present invention provides a bezel pattern
prepared by using the ultraviolet curable ink composition or
manufactured according to the method of forming the bezel
pattern.
[0053] The present invention also provides a display substrate
comprising the bezel pattern. The display may be used in any one
selected from a plasma display panel (PDP), a light emitting diode
(LED), an organic light emitting diode (OLED), a liquid crystal
display (LCD), a thin film transistor-liquid crystal display
(LCD-TFT) and a cathode ray tube (CRT).
[0054] Also, the black bezel pattern according to the present
invention is formed on a hard coating layer or a transparent PI
film included in a cover window of a foldable display. It has
excellent light-shielding properties at a thin thickness so that
the problem of pattern visibility in the panel and visibility
problems due to the stepped portion are not generated. The surface
wrinkling which is occurred due to high light-shielding property
(O.D 5) when single layer printing and UV curing are performed, can
be suppressed by using a light diffusing agent having a high
ultraviolet reflectance. And, excellent thermal stability and
curing sensitivity can be attained by using a long
wavelength-sensitive sulfonium salt photoinitiator as a cationic
photoinitiator. It is possible to perform two-layer printing by the
composition of the present invention. However, if a bezel pattern
is formed on a cover window film by single layer printing,
alignment is not necessary, which is required for two-layer
printing, and thus it leads to improve process time and cost
(yield).
[0055] The present invention will be explained in more detail with
reference to the following examples. The following examples are
intended to illustrate the invention and the scope of the invention
is to be construed as being limited only by the scope of the
appended claims and their equivalents.
EXAMPLES
<Example 1> Preparation of Ultraviolet Curable Ink
Composition
[0056] As shown in the following Table 1, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
butyl diglyme), 7 wt % of Celloxide 2021P, 25 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator (Omnicat 550)
and 6 wt % of GBL were and stirred for 5 hours, to prepare an
ultraviolet curable ink composition of the present invention.
<Example 2> Preparation of Ultraviolet Curable Ink
Composition
[0057] As shown in the following Table 1, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 25 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator (Omnicat 550)
and 6 wt % of GBL were mixed and stirred for 5 hours, to prepare an
ultraviolet curable ink composition of the present invention.
<Example 3> Preparation of Ultraviolet Curable Ink
Composition
[0058] As shown in the following Table 1, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of Al.sub.2O.sub.3, 4 wt % of dispersant, and 30 wt %
of diethyl succinate), 7 wt % of Celloxide 2021 P, 25 wt % of
oxetane OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator
(Omnicat 550) and 6 wt % of GBL were mixed and stirred for 5 hours,
to prepare an ultraviolet curable ink composition of the present
invention.
<Example 4> Preparation of Ultraviolet Curable Ink
Composition
[0059] As shown in the following Table 1, based on the total weight
of the ink composition, a pigment dispersion (15 wt % of carbon
black, 5 wt % of TiO.sub.2, 3.5 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 28.5 wt % of
oxetane OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator
(Omnicat 550) and 6 wt % of GBL were mixed and stirred for 5 hours,
to prepare an ultraviolet curable ink composition of the present
invention.
TABLE-US-00001 TABLE 1 Exam. Exam. Exam. Exam. 1 2 3 4 Pigment
dispersion Carbon black 18 18 18 15 Light TiO.sub.2 5 5 5 diffusing
Al.sub.2O.sub.3 5 agent SiO.sub.2 Acrylic-based 4 4 4 3.5
dispersant Solvent Butyl 30 diglyme Diethyl 30 30 30 succinate BCsA
BCA Epoxy compound Celloxide 2021P 7 7 7 7 Oxetane compound OXT-221
25 25 25 28.5 Adhesion promoting KBM-403 2 2 2 2 agent
Photopolymerization Omnicat 550 3 3 3 3 initiator CPI-210S UV-692S
Irgacure 290 Irgacure 250 Initiator diluent GBL 6 6 6 6 Sensitizer
ITX DBA * Celloxide 2021P: (3',4'-epoxycyclohexane)methyl
3,4-epoxycyclohexyl carboxylate * OXT-221:
Bis[1-ethyl(3-oxetanyl)]methyl ether * KBM-403: 3-Glycidoxypropyl
trimethoxysilane * Omnicat 550:
10-[1,1'-Biphenyl]-4-yl-2-(1-methylethyl)-9-oxo-9H-thioxanthenium
hexafluorophosphate
[Comparative Example 1] Preparation of Ink Composition
[0060] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (12 wt % of carbon
black, 5 wt % of TiO.sub.2, 3 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 32 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator (Omnicat 550)
and 6 wt % of GBL were mixed and stirred for 5 hours, to prepare an
ink composition.
[Comparative Example 2] Preparation of Ink Composition
[0061] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of SiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 25 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator (Omnicat 550)
and 6 wt % of GBL were mixed and stirred for 5 hours, to prepare an
ink composition.
[Comparative Example 3] Preparation of Ink Composition
[0062] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 4 wt % of dispersant, and 30 wt % of diethyl succinate), 7
wt % of Celloxide 2021 P, 30 wt % of oxetane OXT-221, 2 wt % of
KBM-403, 3 wt % of photoinitiator (Omnicat 550) and 6 wt % of GBL
were mixed and stirred for 5 hours, to prepare an ink
composition.
[Comparative Example 4] Preparation of Ink Composition
[0063] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 3 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 27 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 3 wt % of photoinitiator (Omnicat 550)
and 6 wt % of GBL were mixed and stirred for 5 hours, to prepare an
ink composition.
[Comparative Example 5] Preparation of Ink Composition
[0064] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
BCsA), 7 wt % of Celloxide 2021P, 25 wt % of oxetane OXT-221, 2 wt
% of KBM-403, 3 wt % of photoinitiator (Omnicat 550) and 6 wt % of
GBL were mixed and stirred for 5 hours, to prepare an ink
composition.
[Comparative Example 6] Preparation of Ink Composition
[0065] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
BCA), 7 wt % of Celloxide 2021 P, 25 wt % of oxetane OXT-221, 2 wt
% of KBM-403, 3 wt % of photoinitiator (Omnicat 550) and 6 wt % of
GBL were mixed and stirred for 5 hours, to prepare an ink
composition.
[Comparative Example 7] Preparation of Ink Composition
[0066] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 29 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 4 wt % of photoinitiator (CPI-210S) and
1 wt % of sensitizer (DBA) were mixed and stirred for 5 hours, to
prepare an ink composition.
[Comparative Example 8] Preparation of Ink Composition
[0067] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 25 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 4 wt % of photoinitiator (UV692S), 4 wt
% of GBL and 1 wt % of sensitizer (DBA) were mixed and stirred for
5 hours, to prepare an ink composition.
[Comparative Example 9] Preparation of Ink Composition
[0068] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 29 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 4 wt % of photoinitiator (Irgacure 290)
and 1 wt % of sensitizer (DBA) were mixed and stirred for 5 hours,
to prepare an ink composition.
[Comparative Example 10] Preparation of Ink Composition
[0069] As shown in the following Table 2, based on the total weight
of the ink composition, a pigment dispersion (18 wt % of carbon
black, 5 wt % of TiO.sub.2, 4 wt % of dispersant, and 30 wt % of
diethyl succinate), 7 wt % of Celloxide 2021 P, 29 wt % of oxetane
OXT-221, 2 wt % of KBM-403, 4 wt % of photoinitiator (Irgacure 250)
and 1 wt % of sensitizer (ITX) were mixed and stirred for 5 hours,
to prepare an ink composition.
TABLE-US-00002 TABLE 2 Comp Comp Comp Comp Comp Comp Comp Comp Comp
Comp Exam Exam Exam Exam Exam Exam Exam Exam Exam Exam 1 2 3 4 5 6
7 8 9 10 Pigment dispersion Carbon black 12 18 18 18 18 18 18 18 18
18 Light TiO.sub.2 5 3 5 5 5 5 5 5 diffusing Al.sub.2O.sub.3 agent
SiO.sub.2 5 Acrylic-based 3 4 4 4 4 4 4 4 4 4 dispersant Solvent
Butyl diglyme Diethyl 30 30 30 30 30 30 30 30 succinate BCsA 30 BCA
30 Epoxy compound Celloxide 2021P 7 7 7 7 7 7 7 7 7 7 Oxetane
compound OXT-221 32 25 30 27 25 25 29 25 29 29 Adhesion promoting
KBM-403 2 2 2 2 2 2 2 2 2 2 agent Photopolymerization Omnicat 550 3
3 3 3 3 3 initiator CPI-210S 4 UV-692S 4 Irgacure 290 4 Irgacure
250 4 Initiator diluent GBL 6 6 6 6 6 6 4 Sensitizer ITX 1 DBA 1 1
1 * Celloxide 2021P: (3',4'-Epoxycyclohexane)methyl
3,4-epoxycyclohexyl carboxylate * OXT-221:
Bis[1-ethyl(3-oxetanyl)]methyl ether * KBM-403: 3-Glycidoxypropyl
trimethoxysilane * Omnicat 550:
10-[1,1'-Biphenyl]-4-yl-2-(1-methylethyl)-9-oxo-9H-thioxanthenium
hexafluorophosphate * CPI-210S:
4-(Phenylthio)phenyldiphenylsulfonium
tris(pentafluoroethyl)trifluoroethyl)trifluorophosphate * UV-692S:
Diphenyl(4-(phenylthio)phenyl)sulfonium hexafluoroantimonate *
Irgacure 290: Tetralis(2,3,4,5,6-pentafluorophenyl)boranuide;
tris[4-(4-acetylphenyl)sulfanylphenyl]sulfonium * Irgacure 250: 75%
solution of Iodonium, (4-methylphenyl)[4-(2-methylpropyl)phenyl]-,
hexafluorophosphate(1-) in propylene carbonate) * GBL:
Gamma-butyrolactone * ITX: 2-Isopropylthioxanthone * DBA:
9,10-Dibutoxyanthracene
[Experimental Example] Evaluation of Properties of Sample Made from
Ink Composition
[0070] The ink composition prepared in each of Examples 1 to 4 and
Comparative Examples 1 to 10 was subjected to inkjet printing on a
hardcoat film substrate to have an optical density (OD) of 5 by
using X-rite 341C, thereby obtaining a sample. Then, printing
thickness, curing sensitivity, adhesion, inkjet processability
(idle time), surface wrinkling and storage stability of the sample
were evaluated and the results are shown in Tables 3 and 4
below.
[0071] Here, the curing sensitivity was determined by using a UV
LED lamp having a wavelength of 395 nm to detect UV energy at a
tack free point. The adhesion was evaluated as 0B to 5B (Standard:
ASTM D3002, D3359) through cross-cut test. The inkjet
processability was determined by jetting evaluation according to
short purse (3s) and idle time after wiping, with the ink being
discharged from all nozzles. The surface wrinkling was confirmed by
visual observation after UV curing. Storage stability was
determined by checking whether the increase rate of viscosity after
1 week of storage of the sample in an oven at 45.degree. C. was 10%
or less.
TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4
Printing 3 3 3 4 thickness (.mu.m) Optical density 5 5 5 5 Curing
5,000 5,000 5,000 5,000 sensitivity (mJ/cm.sup.2) Adhesion 5B 5B 5B
5B Inkjet 5 min 5 min 5 min 5 min processability (idle time)
Surface OK OK OK OK wrinkling Storage OK OK OK OK stability
TABLE-US-00004 TABLE 4 Comp Comp Comp Comp Comp Comp Comp Comp Comp
Comp Exam Exam Exam Exam Exam Exam Exam Exam Exam Exam 1 2 3 4 5 6
7 8 9 10 Printing thickness 5 3 3 3 3 3 3 3 3 3 (.mu.m) Optical
density 5 5 5 5 5 5 5 5 5 5 Curing sensitivity 5,000 5,000 5,000
5,000 5,000 20,000 10,000 12,000 15,000 6,000 (mJ/cm.sup.2)
Adhesion 5B 5B 5B 5B 5B 5B 5B 5B 5B 5B Inkjet processability 5 min
5 min 5 min 5 min 1 min 5 min 5 min 5 min 5 min 5 min (idle time)
Surface wrinkling OK NG NG NG OK OK OK OK OK OK Storage stability
OK OK OK OK OK OK OK OK OK NG
[0072] From the results of Tables 3 and 4, it can be seen that the
compositions of Examples 1 to 4 according to the present invention
are excellent in curing sensitivity, adhesion, inkjet
processability and storage stability, and does not cause surface
wrinkling, so that there is no reliability problem and it is
suitable for the present invention. On the other hand, the
composition of Comparative Example 1 was the ink in which the
content of carbon black in Example 2 is reduced to 12% and it had a
reliability problem as the bezel thickness increases to 5 .mu.m.
The composition of Comparative Example 2 was the ink in which the
light diffusing agent in Example 2 is changed to 5 wt % SiO.sub.2,
and it had surface wrinkling problems. The composition of
Comparative Example 3 was the ink in which the light diffusing
agent in Example 2 was not contained, and it had surface wrinkling
problems. The composition of Comparative Example 4 was the ink in
which the content of the light diffusing agent TiO.sub.2 in Example
2 is reduced to 3 wt % and it had surface wrinkling problems. The
composition of Comparative Example 5 was the ink in which the
solvent in Example 1 is changed to BCsA, and it had the
deteriorated inkjet processability to 1 minute or less. The
composition of Comparative Example 6 was the ink in which the
solvent in Example 1 was changed to BCA, and it had poor curing
sensitivity (20,000 mJ/cm.sup.2). In addition, the composition of
Comparative Example 7 was the ink in which the photopolymerization
initiator in Example 2 was changed to CPI-210S and it had poor
curing sensitivity (10,000 mJ/cm.sup.2). The composition of
Comparative Example 8 was the ink in which the photopolymerization
initiator in Example 2 was changed to UV-692S and it had poor
curing sensitivity (12,000 mJ/cm.sup.2). The composition of
Comparative Example 9 was the ink in which the photopolymerization
initiator in Example 2 was changed to Irgacure 290 and it had poor
curing sensitivity (15,000 mJ/cm.sup.2). The composition of
Comparative Example 10 was the ink in which the photopolymerization
initiator in Example 2 was changed to Irgacure 250 and it had good
curing sensitivity (6,000 mJ/cm.sup.2) but had poor storage
stability (storage at 45.degree. C. for 1 week, viscosity increase
of 10% or more).
[0073] While the present invention has been particularly shown and
described with reference to specific embodiments thereof, it will
be apparent to those skilled in the art that this specific
description is merely a preferred embodiment and that the scope of
the invention is not limited thereby. It is therefore intended that
the scope of the invention be defined by the claims appended hereto
and their equivalents.
* * * * *